The Marines were part of a group training the Afghan police. While in Afghanistan, they were assigned to a battalion from Camp Lejeune, N.C., although their home base was in Hawaii.

The assailant, identified as Ainuddin Khudairaham, was an aide to an Afghan police chief and had access to the base. Captured quickly, his age immediately became an issue; as with many Afghans, Ainuddin did not possess a birth certificate.

After a bone scan done by Afghan medical personnel to determine his age, an Afghan court decided he was younger than 18 and should be tried as a juvenile.

He was convicted last week and sentenced a day later. For juveniles, seven years and six months is the maximum term for murder, officials said.

The killing came amid a rash of “insider killings” in which U.S. and coalition troops were attacked by Afghans thought to be allies. The Marines were shot while exercising at a gym located in the Afghan police portion of the base.

The killer used an AK-47 and reportedly bragged, "I just did jihad."

Buckley’s family has vowed to continue pressing the case against Ainuddin.

A lawyer for the family also accused the Marine Corps of “abandonment and mistreatment of Gold Star families” by not keeping them fully informed about the court proceedings. The Marine Corps denied the accusation and released a detailed history of efforts to keep the family informed.

“Our approach to supporting the families of our fallen Marines is based on our unwavering commitment to loyalty,” said Marine spokesman Col. Sean Gibson.

A story in the Marine Corps Times described the reaction of Buckley’s father, Gregory Buckley Sr., to hearing the sentencing.

According to the Marine’s aunt, his father spent the night in his son’s bed with a picture of his son, repeatedly apologizing for not doing more to bring the killer to justice.